Magnetic separators are used extensively in many industries to remove magnetic or magnetisable materials, e.g. ferrous contamination, from process materials.
For those process materials which are fluent, it is known to locate tubes across the material flow path and have, magnets located in the tubes so that the contaminant material is attracted to the surfaces of the tubes and retained there. Periodically the flow of material is switched off and the magnets are withdrawn from the tubes allowing the contamination to be released from the walls of the tubes. Traditionally this withdrawal took place manually, but proposals have been made for powered systems using pneumatic rams to withdraw and insert the magnets either under manual control or under the control of some control system. When withdrawn, the magnets do not perform any separator or filtering function and therefore the flow of material must cease prior to withdrawal. Further a hopper or the like is usually disposed across the bottom of the separator so that the released material can fall into the hopper and be removed from the system. Particularly where gases or liquids are involved, significant sealing difficulties can arise.